Abstract: For the launch vehicle tank with multiple constraints such as small central aperture, large girth weld diameter and easy scratching during the inspection process, the traditional film radiography testing technology is still used for girth weld X-ray detection. This process has problems such as low detection efficiency, difficulty in controlling detection quality, difficulty in film storage and high labor intensity for personnel. Through the special installation of small size rectangular detector, semi-circular cantilever structure, detector folding and expansion/contraction mechanism, a digital radiography automatic inspection system has been developed.The inspection image quality meets the A-level requirements of the GB/T 3323.2−2019 standard, the detection results are accurate, the detection efficiency has been greatly improved, and the automatic and digital high-efficiency and high-quality radiographic inspection of the girth weld in tanks with multiple constraints is realized, which strongly supports the rapid and mass production of the launch vehicle tank.